Wave energy converters of this kind, which are sometimes referred to as point absorbers or heaving-buoy wave energy converters, are known from, for example, U.S. Pat. No. 4,277,690. The operation of this particular converter is based on relative motion between, on the one hand, a buoyant body and a so-called acceleration tube attached to and depending from the buoyant body, and, on the other hand, a reciprocable working piston in the acceleration tube; this relative motion is caused by waves of the sea in which the converter operates.
In a wave energy converter of this kind, the working piston and other masses coupled to it form an inertial system which has no positive coupling to the buoyant body and the acceleration tube in the vertical direction, that is, in the direction of the axis of the acceleration tube.
Naturally, the working piston itself and the associated piston rod have a certain mass, but the mass which moves with the piston is determined primarily by the mass of a column of water which is coupled to the piston to move together with it.
In the wave energy converter known from U.S. Pat. No. 4,277,690 an energy-absorbing device for recovering the wave energy includes a double-acting hydraulic piston pump positioned in the buoyant body and connected to the working piston in the acceleration tube through a piston rod. The piston rod is in some respects a critical component.